Yep thats right..you just order a timing set for a 70 or earlier car 390.. and they dont have have factory 4* retard in them.. They are set for zero..So most of your cams today come with 4* advance ground into them (depending on manufacturer)

The truck motors didnt need any advance as they are a low comp motor...you cant feed a PIG thats not hungry!!

RJ

 

I put the timing gears at 4 degrees advance on the 390 FE. Plan on pulling the timing cover off to replace the round dish on cam for fuel pump.

I wonder what setting the timing gears to zero would do for the crane cam 343901/engine?

 

But what if the cam is ground retarded? A simple replacement timing set for a '72 and earlier would help, but not enough to bring the timing back to zero. This is why it's not enough just to say "'72 and earlier timing set".

You need one with lots of adjustment, and a degree wheel.

 

Just wondering if anyone knows the timing grind in the Crane Cam 343901? 0 degree or 4 degrees?
The spec sheet for this cam calls for start year 1963 to 1976, Ford & Mercury, 8 cylinder, 352-428 CI.

 

The Crane 343901 is ground 1 degree advanced.

 

Next time I pull the timing cover off, I plan on setting the Coyles Timing gear set to zero degrees.

 

I meant with a completely stock (original) motor, a decent performance upgrade, without playing with the cam and lifters, would be to get a pre-72 timing set.

I don't think Melling or anyone else making stock-replacement cams grinds them differently than Ford did, do they?

(well, maybe more accurate, but retarded/advanced? They'd be asking for trouble)

 

Well yeah, Crane and Comp might grind a little advance / retard into them (usually 4 degrees advanced). But I thought we were talking about the stock cam here? It was my understanding that Ford ground a lot of retard into the stock cam itself, to help with emissions, in addition to messing with the timing set.

 

That I'm not sure about - I've read here over the years, and from my machinist, that the stock timing set was the only difference.

But what do I know?

 

What timing advance do these FE engine like running at?

 

If the stock timing set is retarded or advanced, the timing dot will not be in line with the cam dowel or the dot on the crank gear will not line up with the crank key. If the cam itself is anything other than straight up, you will never know unless you degree the cam.

 

Cool! :)

Cool thread too huh? :)

For the most part... i don't know nuthin. :/
I'm not a V8 engine re-builder... only motorcycle and VW engines. :/

I've experimented with 4 stroke motorcycle cam timing tho. Throughout the 70's there was a whole bunch of Honda 100cc and 125cc engines that would rev great but wouldn't idle or ever settle down at idle. I wollered out the cam sprocket holes with a 1/4" rat-tail file and advanced the cam.

"hammer mechanic" style of degreeing a cam. :)

They ran fine if you had room to keep them rev'ed up but for "observed trials" type-riding, they were a friggin nightmare. :) I fixed that on a whole bunch of them with my rat-tail file. ;) The mechanic at the Honda shop was mighty interested in what I'd fiNgured out. :) He started doing that to fix the same complaints I had-had with my wifes brand new motorcycle, not idling worth anything and having no-low-end-power. :)

He couldn't/wouldn't fix it, so I did, is all.

Advanced cam timing (in relation to the crank and piston position) makes it run more like a tractor. Retarded cam timing makes it run more like a dragster.

I sounds backwards until you picture how the words are describing "in relation to" piston-position. Then it seems clear what's really going on... retarded and advanced would switch places if you thought in terms of the valves controlling everything else instead of the crank being in "control".

The crank really does follow what the valves/cam tells it to do, like run backwards even, in the case of some boat engines or a Corvair engine bolted up to a VW trans-axle. :)

Cool way to see an engine tho huh? :)

When i hit upon that one day, the whole vision of an engine changed for me... the crank and pistons are slaves, not masters.

Only in a situation like this (engine forum) can something that crazy sounding even be mentioned. :)

Crank timing is very convenient and so everything has standardized around it?

--------------------

Then there's how far the valve opens (lift) which i never felt like I really understood.

My 252/252 Comp "economy" cam has a high lift in comparison to its duration, which is supposed to be for lower rpm power, right? My 360FE will idle nice and smooth at 380rpm (part of that's carb work) if I want it to.

And how all this effects the octane rating needed by the engine is another weak spot of mine. :/

Alvin in AZ

 

I can help there.

Cam duration is a lot like your observed cam timing differences. Less duration means more low end tractor like power. More duration means more top end dragster like go-power. Here's why.

Valves are really timed at certain events. When they open, and when they close being the two big ones. In all cams that I know of, the valves open before you would think they should, and close after you'd think they should shut. Airflow is the reason for this. In a running engine, the airflow actually has quite a bit of mass. The air flowing down the intake runners builds up momentum, and wants to flow past the intake valve. By opening the intake valve before TDC, the air gets that opportunity and you get extra cylinder filling. This also happens with the exhaust valve. By opening the exhaust valve before BDC, the extra cylinder pressure gets to blow extra exhaust out the cylinder, and with the help of exhaust tuning actually drawing extra exhaust out of the cylinder and creating a bit of a vacuum. The exhaust then stays open a bit past TDC to allow any flowing exhaust gasses a chance to leave.

Lift is simply like it sounds. How far the valve lifts off it's seat. Obviously, farther the valve lifts, the bigger the opening, and the greater potential for airflow. The more airflow at any given rpm, the more power.

So a cam with more lift will usually give you more power than one with less lift. Obviously there are exceptions to this involving complex airflow, which I wont get into here.

How does all this have to relate to compression? Easy. The one event I didn't talk about above is the IVC (intake valve closing) event. Something special happens here at lower RPM's. The intake valve is closed some number of degrees after BDC, bottom dead center, on the compression stroke. At low RPM's when you dont have enough airflow, some of the compression is actually bled back off into the intake. That's right, it reverts and goes back the other way. So what you've done is essentially reduce the swept volume of the cylinder! Now when you do that, and combustion volume stays the same, the compression ratio is lowered. This is where we get the term "dynamic compression." Then, when the RPM's pick up to a point where airflow takes over, you get all your compression back and a nice increase in power.

This is why we can run high compression with big cams. It's not the overlap cooling things down or anything goofy like that, although that may have some small affect. It's all about the intake valve closing angle.

Now what happens when we run a low compression motor with a big cam? Well, at low rpm's, more air and fuel is bled off back into the intake. The effective compression ratio lowers. But since it was already at a low value, we've just lowered it a lot more. Now we have an engine that we refer to as a "dog". Some "replacement" or "RV" cams, such as Melling, come to mind. They market the cams as stock replacement, but use way too much duration. People put these in their stock motor then wonder why it sucks.

Sorry for the book.

 

What do you guys think about a stock profile cam of that of a 390GT/428CJ,SCJ? Someone told me that this is a great cam to use for mileage and all around street performance. Just looking for a cam that will run in a 9.5:1 compression 390, D2TE-AA heads, four barrel induction and headers in a small half ton 2wd truck.

 

rusty, maybe you should write books on this stuff cause that was first thing that I have understood all week